Add more weapons, cause they getting cool. Add more gizmos.
Laser for weapon and guided laser for gizmo.
Magazine, for if you want to make a custom cannon.
Add custom weapons, so you can make your own without having to download one from someone else, and you don’t have to wait until someone has the same idea as you for a weapon.
War mode, were it’s like constant battle, to test out weapons in a more fun way against ai.
Multiplayer, game modes, constant war (so infinite deaths to test weapons on a more fun way against ai and players With all the veichles you can build), veichle, navy, planes, no physics mode (so you can build what ever you want and fly it about or sail it or drive it without having to worry about anything), keep physics mode (cause it’s fun).
Custom sounds, custom weapons, custom gizmos, multiplayer, none physics mode, keep physics mode, constant warfare with ai with custom maps and navy and everything cool(just make everything custom), glass cockpits, and just add really cool stuff like nukes, custom navy and custom airports.
Bigger fleet as well. Command ai for battles and stuff, (so you can spawn planes, and command them to do stuff, like attack, defend, follow, run away, land, take off, scout, fall back to next defence, etc....), ad defences, (like, custom maps, so you can place AA guns in places, hostile airports that would send stuff to kill you, tanks, soldiers (little people), citizens, buildings (like cities, military, villages, airports, ship ports, beaches, factories, farmland), space (solar system only, real distance mode and short distance mode,)
Aliens for space (space ship stuff, space weapons, hyper space gizmo and engine, alien stuff) and finally add a first person mode, like you spawn as a person walking about, spawn in a plane get into the plane and fly about, get into a ship sail, get into a veichle and drive or get into a defence weapon or anything the player has built). Thanks for reading this if you did. There are still a lot more I want, but I’ll say if you don’t add them, and on another time, so you don’t have to much to worry about.
If you want more "alien stuff" vote for my propulsion suggestion: https://jundroo.uservoice.com/forums/221664-jundroo-games/suggestions/42382924-more-propulsion-options
It proposes various systems that you are talking about. Some of the examples are:
-direct impulse propulsion (like particle accelerators)
-laser thermal rocket propulsion
-microwave thermal rocket propulsion
For example if you're a fan of star trek, the main ships are propelled by anti-matter. Star wars hyperdrives like u say with "hyperspace gizmos" allow ships to reach the speed of light. Using a combination of anti-gravity and anti-matter propulsion you could make this in SimplePlanes.